1. Field of the Invention
The present invention relates to a high-speed actuating device suitable for actuating a switching device between two switch positions in very short switching times, having the features of the preamble of Claim 1.
2. The Prior Art
In certain applications, a mechanical switching device must be actuated between two switch positions within an extremely short switching time. For example, German Patent DE 37 37 824 A1 describes a method of operating an internal combustion engine. This internal combustion engine has an intake channel leading to at least one combustion chamber of the engine, at least one intake valve which is situated between the intake channel and each combustion chamber and determines the start of intake and the conclusion of intake into the combustion chamber and an additional valve situated upstream from the intake valve. According to the known operating method, this additional valve is opened when the intake valve is opened and is closed temporarily during a period of time that maintains an interval from the beginning of intake to the end of intake. Due to this procedure, dynamic effects in the intake stroke of the piston being actuated in the respective combustion chamber can be utilized to increase the loading of the combustion chamber with fresh air. In addition, definitely shorter opening times, in particular a plurality of opening times, can be implemented within the opening period of the intake valve through appropriate operation of the additional valve, and these opening times can also be shifted toward “early” or “late” relatively arbitrarily within said opening period. To this extent, with the help of the additional valve, which can be operated appropriately, it is possible to implement variable valve control units even if the actual valve control, e.g., by means of a camshaft, is invariant per se.
To open and close the additional valve during the opening time of the intake valve(s) once or more, very short switching times must be implemented for the additional valve. The switching times required to accomplish this amount to about 2 ms in this specific embodiment. Switching times of about 10 ms can be achieved with traditional electric motors.
International Patent WO 98/42953 discloses a high-speed actuating device having two switchable electromagnets between which is arranged an armature that is drive-coupled to the switching device, which is designed as an intake valve or exhaust valve of an internal combustion engine. In the first switch position of the valve, the armature is in contact with the one electromagnet, while in the second switch position, it comes to rest against the other electromagnet. The armature here is connected by way of a connecting part to a rotating rod, which is rigidly clamped on a stationary component of the actuating device. An operating element is mounted on the armature, cooperating with the valve for at least an opening stroke. The known high-speed actuating device serves here as a valve drive in an engine with which variable control times for the respective valve can be implemented. At a high rotational speed of the internal combustion engine, actuating times of approximately 3 ms can be achieved with the help of such a high-speed actuating device.
However, there is a demand for a high-speed actuating device with the help of which it is possible to implement even shorter switching times. For the other type of application mentioned above for operation of an additional valve, this means, for example, shortening the switching times by at least 30%.
U.S. Pat. No. 5,131,365 describes a high-speed actuating device of the type defined in the preamble, which is suitable for adjusting a switching element designed as a switching flap between two switch positions with very short switching times. The switching valve is situated in a gas-carrying line, namely in an intake channel of an internal combustion engine upstream from an intake valve; in a first switch position, it can close off the line cross section, and in the second switch position, it can open the line cross section. With the known high-speed switching device, the switching flap is prestressed in its closed position with the help of a prestressing spring. An electromagnet is provided, holding the switching flap in its closed position, so that in the filling stroke of the piston, a vacuum pulse can be built up on the cylinder end. As soon as the electromagnet releases the switching flap, the vacuum on the cylinder end causes the switching flap to open. As soon as the pressure on the switching flap is equalized, the restoring spring can adjust the switching flap back into its closed position in which it can then be held again by the electromagnet. The known high-speed actuating device thus operates passively, namely as a function of the piston movement. However, it would be desirable to have a high-speed adjusting device which can be used much more flexibly and nevertheless permits extremely short switching times.
British Patent 1,572,299 discloses another high-speed actuating device with the help of which a deflector plate can be switched between two end positions. This deflector plate works as a shunt in a conveyor zone for bulk printed matter or the like and is drive-connected via a shaft to an armature. This armature is rotatably adjustable about the longitudinal axis between two electromagnets.